A 15-point index including both conventional and newly identified risk factors for the conditions correctly classified 88 percent of patients according to their risk of developing dementia within six years, Deborah Barnes of the University of California San Francisco and colleagues reported online in Neurology.

More than half of patients with a high score -- 56 percent of them -- developed some form of dementia, compared with 4.2 percent of those with a low score and 22.8 percent of those who fell in between.

Alzheimer's Disease: Listing Out the Risk Factors

The factors included in the index that best predicted whether a patient would develop dementia were older age, lower scores on two tests of cognitive function, presence of at least one of the known genetic variations linked to Alzheimer's, below-normal weight, abstinence from alcohol, a history of coronary artery bypass surgery, and a slow time putting on and buttoning a shirt -- a test of fine motor function.

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The researchers also included in the index certain changes in the brain and arteries that could be detected through medical imaging.

A low score on the index might reassure patients and their families, the researchers said, and a high score might aid patients in making preparations for the future.

But Zaven Khachaturian, president and CEO of the Lou Ruvo Brain Institute in Las Vegas and a widely recognized authority in Alzheimer's Disease, said that before the tool could be used in clinical practice, physicians and patients would need more information about how to interpret the scores.

Alzheimer's Index Not Ready for Clinical Use

"At this stage, it would be prudent to use this test as a research tool, rather than as means to manage patients in general medical practice until further validation of the predictive utility of the test," he said.

Still, there are currently no tools to predict dementia risk late in life, Barnes and her colleagues said. A midlife index exists, but it assesses risk over the next 20 years.

To fill the gap, the investigators used data from 3,375 patients 65 and older who took part in the Cardiovascular Health Cognition Study. All were free from dementia at the beginning of the research.

Through six years of follow-up, 14 percent developed some form of dementia. Of those, 51 percent were diagnosed with Alzheimer's disease, 13 percent with vascular dementia, 31 percent with mixed dementia, and 5 percent with other types.

The index correctly identified patients who would experience dementia 56 percent of the time, and it was able to correctly rule out a person for dementia 90 percent of the time. All told, the test yielded the correct answer 88 percent of the time over the six years encompassed by the research.

This late-life index is slightly more accurate than the midlife index, which "may suggest that it is easier to predict dementia risk closer to symptom onset," the researchers said, "or it may be a function of the relatively simple measures used in the midlife index."

For Dementia, Lack of Early Warning a Problem

A major challenge for the study of dementia, Khachaturian said, is the inability to detect the disease in the early stages, before a patient has any symptoms. A tool like the one developed by Barnes and her colleagues could potentially solve this problem.

But Dr. Steven DeKosky, dean of the University of Virginia's School of Medicine, suggested that the tool would be most helpful once effective preventive medications are developed.

"Then it will be very useful to have simple, non-invasive ways of identifying people at greater or lesser risk of developing the disease," he said.

Alzheimer's Disease: Knowledge Could Be Helpful

Dr. Samuel Gandy of the Mount Sinai School of Medicine in New York, noted, however, that "nothing currently available offers meaningful sustained slowing of progression" -- in other words, even if patients knew to expect Alzheimer's there would be little to nothing they could do about it.

Still, if the index is proven in other studies to be effective, Barnes said, it could prove helpful in a clinical setting by identifying "people who have no signs of dementia but should be monitored closely, allowing them to begin treatment as soon as possible, and potentially helping them maintain their thinking and memory skills and quality of life longer."

This article was developed in collaboration with ABC News.

The study was supported by grants from the National Heart, Lung, and Blood Institute and the National Institute on Aging. Additional support was provided by the National Institute of Neurological Disorders and Stroke and an NIH/National Center for Research Resources UCSF-CTSI grant. Barnes receives funding through a Career Development Award from the NIH.

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